Tread link



June 14, 1932. A. P. ARMINGTON 1,862,617

TREAD LINK Filed Oct. 27, 1931 2 Sheets-Sheet l INVENTOR 14577905EAFMWGTO/l/ ATTORNEYS June 14, 1932.

A. P. ARMINGTON TREAD LINK 2 Sheets-Sheet 2 Filed Oct. 27. 1931 INVENTORJFTHVAPJ/F/W/A/GTQV ATTORNEYS Patented June 14, 1932 UNITED STATESPATENT OFFICE ARTHUR P. ARMINGTON, OF WILLOUGHIBY, OHIO, ASSIGNOR TO THEEUCLID ROAD MA- CHINERY COMPANY, OF EUCLID, OHIO, A CORPORATION OF OHIOTREAD LINK Application filed October 27, 1931.

This invention relates to endless tread linkages of truss-forming orbeam-forming type, such as those employed in connection with pairs ofidler wheels to form the so-called track-laying wheel substitutes.

It is in the stretches of the linkage between wheels, and particularlyin the lower, ground-engaging stretch, that the beamforming or trusscharacteristic is desired.

Hereinafter is considered specifically only the ground-engaging stretch,and unless otherwise stated, links are assumed as being therein.

The loading upon the ground-engaging stretch of the linkage, if theground be soft, is somewhat distributed throughout the stretch betweenleading and following wheels. Repeatedly, however, even in soft earththe linkage is run over projections such as boulders, in which event theloading on the stretch is characteristically that of a concentrated loadtraveling along a beam. And where the stretch has curvature and thelinkage is moved over hard earth as a pavement, the loading ischaracteristically a concentrated one fixed at the center of thestretch.

It will be apparent that the maxlmum stresses in a stretch will benormally at the center of the stretch, as when the stretch hascurvature, and occasionally will move along the stretch as when thelinkage is run over a projection; and this is true both of thecompression members in a stretch, the shoe portions and pins, and of thetruss members of the links. The primary forces imposed upon the stretchare the downward forces of the two wheels at the ends of the linkage,and the upward force of the supporting surface, normally at the centerof the stretch although under certain conditions, elsewhere along thestretch. Thus as a link moves relative to its stretch from one end tothe other thereof,

Serial No. 571,377.

lugs of the links is not perfect, and since the linkage is operatedunlubricated, in sand, mud, and generally under the most adverseconditions, wear is bound to develop more or less rapidly at the pins.

An object of my invention is to minimize this wear, by eliminatingtranslatory motion of the links upon their pins when the latter areloaded.

Where the truss members are rigidly associated with the other parts oftheir links, and particularly where the abutting faces of the trussmembers are disposed in vertical planes, any lost motion at the hingepins will allow an equal sliding motion between these abutting faces asthe described vertical forces are reversed in the stretch of linkage.And since this sliding occurs when the faces are bearing against eachother with maximum pressure, wear upon the faces is tremendous. Suchwear is highly undesirable as it results in a loss of curvature of theground-engaging stretch, ultimately allowing the stretch to sag upwardlybetween the wheels.

Another object of my invention is to eliminate this wear betweenabutting faces of the truss parts, by so arranging the parts that therewill be no motion between these faces when they are in abuttingrelation.

Briefly, the objects of my invention are ac complished by the simpleexpedient of ar ranging the faces of the truss parts inslop ing planesso related with the hinge pins that when a link is functioning in astretch of linkage, the sum of the opposite resultant forces in saidfaces due to their cooperative connection will be less than the frictiontherebetween, as the links progress through the zone of maximum stressin the stretch; and more directly with reference to the pins, therelation of parts is such that the forces exerted upon a pin do notmaterially change direction throughout the zone. In other words, the endportion of one link will act as a wedge upon the near end portion of thenext link, to maintain the position of the parts relative to the pinjoining them; the wedging action will be initiated to seat the parts atthe beginning of the stretch, and will continue and prevail upon thepins substantially throughout the stretch.

The exact nature of this invent-ion together with further objects andadvantages thereof will be apparent from the following description takenin connection with the accompanying drawings, in which Figs. 1, 2 and 3are plan view, and end and side elevations respectively of a linkembodying my invention; Fig. 1 is a conventionalized showing of' alinkage made up from improved links as shown in Figs. 1 to 3, partsbeing shown in section, and Fig. 5 is a showing similar to Fig. 3 butwith parts broken away and with forces indicated as acting upon the linkwhen the latter is in a. stretch.

With reference now to the drawings and particularly Figs. 1 to 3thereof, the shoe or tread ortion 1 of the link is lowermost, having aottom ground-engaging surface 2 and thereabove a pair of rail sections 3for supporting wheels. The shoe portion has hingepin-receiving openings4 at its ends, located in the usual projectin lugs 5, which latter arestaggered so that a pair of links may be joined her 7 is preferablyabove the shoe portion and the member 6 overhangs the latter asindicated to provide better clearance at the bights of the linkage. Theeye member 7 is supported by the webbing indicated, forming a canopywithin which the hook member 6 of an adjacent link ma move about the pinconnecting the links. he arch of the canopy may be strengthenedbyupstanding flanges 10, and various clearance openings such as at 11 areprovided for extrusion of accumulated foreign matter and as at 12 forfoundry convemence.

The faces 8 and 9 are flat and arranged in sloping planes. The plan ofthe face 8 is one which passes between the hinge-pin openings 4 on theopposite ends of the link, and preferably substantially equidistanttherefrom. The plane of the face 9 is substantially parallel with thatof the face 8. Exact parallelism would result in all of the openings 4lying in the same plane in a stretch of the linkage, which is notdesirable. Therefore, preferably the plane of the face 9 is slightly outof parallel, converging upwardly toward that of the face 8, so that thepitch spacing of the faces 8 and 9 is slightly less than that of theopenings 4, and the stretch of linkage has a slight curvature.

With reference now to Fig. 4, a linkage of my improved links such asappear in Figs.

1-3 is shown. Here the links are shown as connected by greatlyundersized hinge pins 14., and the forces imposed upon the stretch arethe downward forces B and C at the ends and the intermediate upwardforce A. It will be seen that all of the pins 14 assume the sameidentical position relative to adjacent parts, throughout the stretch.There is, therefore, no motion either of the pins or thereabout in thestretch, and this is true although the vertical forces upon the linksare reversed as the point of maximum stress, at A, is passed. Neither isthere relative motion between the abutting faces of the hook and eyemembers 6 and 7 In fact it is because of the sloping planes of thesefaces,

and their relationship with the hinge pins,

that there is no motion; for throughout the stretch there is a wedgingaction of each link upon both its adjacent links tending to jam andmaintain the pins in the relative positions shown. And the result isthat the relationship of the links throughout the stretch is constant asindicated in the line 16.

This may be illustrated with reference now to Fig. 5, assuming the linkshown to be one functionin in the stretch as in Fig. 4. At the left endof the link the force D is impressed upon the face 8 by the nextfollowing link acting as a bellcrank about the pin in the correspondingopening 4. Similarly, at the opposite or forward end, the force isimpressed upon the face 9 by the link next ahead. These forces, however,do not act perpendicularly to the faces 8 and 9, as has beencharacteristic of the prior art. Instead, they act perpendicularly tothe planes of their hinge pins, as indicated by the dot-dash lines, Fig.5, and thus obliquely to the faces 8 and 9. Consequently they have camaction upon the faces, to maintain the link in the relation indicated inFig. 4.

The hook member 6, therefore, acts as a wedge to jam between theadjacent hinge pin 14 and the eye member 7 of the adjacent link, againstwhich the hook member bears; and the force of this wedging action issufficient that, as the link progresses through the zone of maximumstress, intermediate the ends of the stretch, the force A does notaffect the position of the hinge pin, or, what is more important, therelative positions of the abutting faces.

\Vhat I claim is:

1. In a tread link of the class described and having a shoe portion withhinge means at its ends, and truss members extending upwardly, saidtruss members having faces adapted to abut corresponding faces ofadjacent similar links connected by hinge pins in a stretch of linkage,to impart beam characteristics to the stretch, said faces being soinclined with reference to the location of said hinge means that whilethe linkage progresses through the zone of maximum stress intermediatethe ends of said stretch, said faces will cooperate with camcharacteristic to maintain substantially constant the direction ofresultant forces acting upon said hinge pins.

2. In a tread link of the class described and having a shoe portion withhinge means at its ends, and truss members extending upwardly, saidtruss members having faces adapted to abut corresponding faces ofadjacent similar links in a stretch of linkage to impart beamcharacteristics to the stretch, said face of one of said truss membersbeing arranged in a plane which passes between the hinge means on theopposite ends of said link, and said face of the other member beingsubstantially parallel with said plane.

3. In a tread link of the class described and having a shoe portion witha hinge at each end, and truss members extending upwardly, said trussmembers having faces adapted to abut corresponding faces of adjacentsimilar links in a stretch of linkage, to impart beam characteristics tothe stretch, said face of one of said truss members being arranged in aplane which passes substantially equidistant between the hinges on theopposite ends of said link, and said face of the other truss memberbeing substantially parallel with said plane.

4. In a tread linkage of the class described, a pair of links havingshoe part-s, hinge means connecting said parts for relative coaxialmotion, said links having truss-forming parts upstanding from said shoeparts when the latter are in ground-engaging position, saidtruss-forming parts having faces interengageable to limit said motion inone direction, said faces being arranged to define by interengagement,when said tread parts are in said position, a sloping generallytransverse surface, from the mean plane of which said hinge means issubstantially removed, whereby when forces are applied to said links tocause interengagement of said faces, as in a ground-engaging stretch ofsaid linkage, said limiting engagement of said faces will havecoincidental cam characteristic efiective at said hinge means tomaintain the direction of resultant forces acting thereuponsubstantially independent of vertical forces imposed in the functioningof said linkage through said stretch.

In testimony whereof I hereby afiix my signature.

ARTHUR P. ARMINGTON.

